We've seen music sequencers in the past, but nothing that rivals the BeatBearing for simplicity and number of balls. The unit was designed by Peter Bennett during his studies of new techniques people can use to interact with musical instruments.
Sequences are composed by placing the metal orbs in a grid of receptor cups which represent the different rhythm tracks (kick, snare, hi-hat and cowbell) along the vertical axis, and beats along the horizontal.
So it works like any other sequencer, but with balls. And let's face the facts people: balls make everything awesome. I have balls and I'm awesome. Pinball machines, ballpits, and ballgames are all awesome. The balls on that chick from last ni -- oh god no.
A worthwhile video of the thing in action after the cowbell.
music sequencer has balls of steel [technabob]